JPS62180708U - - Google Patents

Description

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an AC bridge power supply for a strain measuring instrument showing one embodiment of the present invention, Fig. 2 is a circuit diagram showing another embodiment of a variable gain amplifier, and Fig. 3 is a circuit diagram showing another embodiment of the variable gain amplifier. FIG. 4, a circuit diagram showing another embodiment, is a characteristic diagram showing an example of temperature-amplitude change (%) characteristics of the oscillator and variable gain amplifier of the circuit of FIG. 1. 1... Oscillator, 2... Variable gain amplifier, 3...
Transformer, 5...detection section, 8...rectifier circuit, 9...
... Smoothing circuit, 10 ... Error amplifier, 11 ... Reference voltage circuit, 13 ... Light emitting element, 14 ... Photoconductive element, 15 ... Feedback resistor, 17 ... Input resistance.

Claims (1)

[Claims for Utility Model Registration] (1) A signal output from the output terminal of a detection section consisting of a Wheatstone bridge including a strain gauge is connected to an input transformer, a carrier wave amplification circuit,
A sine wave generated by an oscillator is transmitted via an amplifier to the input terminal of the detection section in a strain measuring instrument that converts the measured value into a measured value using a phase detection circuit, carrier wave filter circuit, DC amplifier circuit, A/D converter, etc. and displays or records it. In the supplied AC bridge power supply circuit for strain measuring instruments, the amplifier is a variable gain amplifier consisting of an operational amplifier whose gain is controlled by an input resistance element or a feedback resistance element, one of which is a variable resistance element, and one of the variable gain amplifiers is an input end is connected to the oscillator directly or via the input resistance element, an output end thereof is connected to the primary coil of the transformer, and is connected to one input end of an error amplifier via a rectifier circuit and a smoothing circuit, The DC output output from the smoothing circuit corresponding to the output of the variable gain amplifier is compared with the output of a reference voltage circuit connected to the other input terminal of the error amplifier, and the output from the error amplifier is applied to a light emitting element. and the input resistance element or the feedback resistance element, which is a variable resistance element for gain control of the variable gain amplifier, is a photoconductive element that converts a change in brightness irradiated onto the light emitting element into a change in resistance value, and A secondary coil of a transformer is connected to the input end of the detection section, and a sinusoidal AC output voltage having a constant amplitude output from the variable gain amplifier is supplied to the input end of the detection section via the transformer. An AC bridge power supply circuit for a strain measuring instrument, characterized in that it is configured as follows. (2) The alternating current for strain measuring instruments according to claim 1, wherein the variable gain amplifier has a configuration in which a photoconductive element is inserted as a gain control resistive element between the inverting input terminal of the operational amplifier and the ground. Bridge power supply circuit. (3) The alternating current for strain measuring instruments according to claim 1, wherein the variable gain amplifier has a configuration in which a photoconductive element is inserted as a gain control resistive element between the inverting input terminal of the operational amplifier and the oscillator. Bridge power supply circuit. (4) The AC bridge power supply circuit for a strain measuring instrument according to claim 1, wherein the variable gain amplifier has a configuration in which cadmium sulfide is used as a feedback resistance element of the operational amplifier.